1. Field of the Invention
The present invention relates to a drive transmission mechanism for transmitting a drive force to processing means and a cartridge provided with such a mechanism, which are preferably used in an electrophotographic image forming apparatus, such as an electrophotographic copying machine or an electrophotographic printer.
In this connection, the electrophotographic apparatus is an apparatus for forming an image on a recording medium 52 by utilizing an electrophotographic-image-forming process.
The electrophotographic image forming apparatus includes, for example, an electrophotographic copying machine, an electrophotographic printer (e.g. an LED printer and a laser printer, etc.), an electrophotographic facsimile machine and an electrophotographic word processor etc.
What is referred to by the term “cartridge” is, for example, a cartridge formed as a unit including a photosensitive drum for electrophotography, serving as an image bearing member and at least one of charging means, developing means and cleaning means, which is adapted to be detachably attached to a body of an image forming apparatus.
2. Related Background Art
Conventionally, an image forming apparatus such as a copying machine, a printer, a facsimile machine etc., that utilizes an electrophotography system of a transferring type includes a photosensitive member serving as an image bearing member, generally in the form of a rotary drum, a charging apparatus (performing a charging process) for charging the photosensitive member uniformly with a prescribed polarity and up to a prescribed electric potential, an exposing apparatus (performing an exposing process) serving as information writing means for forming an electrostatic latent image on the photosensitive member that has been processed to be charged, a developing apparatus (performing a developing process) for visualizing the electrostatic latent image that has been formed on the photosensitive member with a developer in the form of a toner, a transferring apparatus (performing a transferring process) for transferring the toner image from the photosensitive member to a transferring material such as a paper sheet, a cleaning apparatus (performing a cleaning process) for removing the toner somewhat remaining on the photosensitive member after the transferring process to clean the surface of the photosensitive member, and a fixing apparatus (performing a fixing process) for fixing the toner image on the transferring material, etc. The photosensitive member is subjected to the electrophotography process (including the charging, exposing, developing, transferring, and cleaning processes) repeatedly for forming an image.
The toner remaining on the photosensitive member after the transferring process is removed from the surface of the photosensitive member by the cleaning apparatus so as to be stored as waste toner. From the viewpoint of environment protection or the effective utilization of resources, it is preferable that the generation of such waste toner be eliminated.
In view of this, some image forming apparatus return the transfer residual toner (i.e., so-called waste toner) collected by the cleaning apparatus to the developing apparatus for reuse or recycling.
On the other hand, it has been proposed to do away with the cleaning apparatus to make an image forming apparatus a cleanerless system. In the cleanerless image forming apparatus, the transfer residual toner remaining on the photosensitive member after the transferring process is removed and recovered for reuse by cleaning simultaneous with developing.
For such an image forming apparatus, U.S. Pat. No. 6,421,512 proposes a structure having toner-charge-amount-control means for imparting an electrical charge to the transfer residual toner to control the charge amount of the toner, so that the toner is recovered and reused by the developing apparatus.
In such an apparatus, if a fixed brush-like member is used as the above-mentioned toner-charge-amount-control means to control the tribo (triboelectricity) of the transfer residual toner to an appropriate charge amount with a normal polarity, slight overcharging of the transfer residual toner sometimes occurs. When the overcharging of the transfer residual toner occurs, the mirroring force of the photosensitive member and the overcharged toner is so strong that the toner does not adhere to the contact charging apparatus, recovered by the developing apparatus, nor is it transferred by the transferring means. Consequently, the toner will melt and adhere to the surface of the photosensitive member to produce a defective image.
It turned out that the cause of the above problem was that the fixed brush-like member as the toner-charge-amount-control means continues to stay at the same position on the photosensitive member. Specifically, when the resistance of the toner-charge-amount-control means is uneven, either overcharging or insufficient charging occurs at the same position on the photosensitive member. In the area in which the overcharging is occurring, the above-mentioned problem of the slight overcharging of the transfer residual toner and its adhering on the surface of the photosensitive member would arise. On the other hand, in the area in which the insufficient charging is occurring, another problem that the contact charging member is contaminated with the toner adhering thereto due to insufficient charging of the transfer residual toner would arise.
With the recent diversification of user's needs, successive printing of images having high coverage rates (such as photographic images) is sometimes performed. In addition, with the development of color printing, a multiple-developing process is applied to the photosensitive member. These processes generate a large amount of transfer residual toner at one time, which exaggerates the above-mentioned problems.